Mary Boyce

The perspective of Mary Boyce, who has died aged 85, on Zoroastrianism, the world's first monotheistic religion, was transformed by a year of fieldwork in 1966 among orthodox Zoroastrians in remote villages around the desert city of Yazd in central Iran.

What she discovered there led her to question many scholarly assumptions about the prophet Zoroaster and his followers. Who, she asked, was best able to interpret the teachings of the prophet, almost three millennia ago: western scholars in the comfort of their studies, or the practitioners of the religion living in a remote region free from outside influences?

She contended that in non-literate societies ancient practices are preserved with greater fidelity than are teachings in a literate society. She thereby constructed a picture of the continuity of Zoroastrianism, starting with the priestly tradition into which Zoroaster had been born and trained, and progressing through the millennia so that the beliefs and practices of modern Iranian Zoroastrians, untainted by western and urbanised living, could be used to interpret ancient texts.

She came to appreciate the importance of ritual devotions and traced them back to the life and teaching of the prophet, indeed into pre-Zoroastrian times. Previously, influenced by studies of Christianity which contrasted "faith and works" and Protestant perspectives on the growth of Christianity, scholars had depicted Zoroaster's followers as falling away from the pure abstract philosophy of the founder, returning to pre-Zoroastrian pagan practices under the superstitions of faithless priests.

She presented her research findings in her Ratanbai Katrak lectures at Oxford University in 1975 and published them as A Persian Stronghold of Zoroastrianism (1978). Her love for the people among whom she lived and worked shines forth in her publications, and through that deep bond of friendship she came to radical reinterpretations of the standard books on Zoroastrianism. She was also greatly amused that the Persians thought she was the daughter of Edward Browne, a scholar who had embarked on a similar journey of discovery almost a century before.

Mary, professor of Iranian studies at London University's School of Oriental and African Studies (Soas), was one of the last century's leading scholars in her field. I started my postgraduate studies at Soas under her supervision within days of her return from Iran; it was exciting to be a student of a scholar beginning to explore new thoughts and rejecting received scholarly thinking.

The first book to present this dramatically revised history was Zoroastrians: Their Religious Beliefs and Practices (1979) which, with her anthology of texts from different Zoroastrian eras, became the standard works for students around the world. Her magnum opus is a multi-volumed History of Zoroastrianism (1975, 1982, and 1991). Sadly, she died before completing the fourth volume, on the Parthian period, though her work is to be continued by Albert de Jong of Leiden University.

She was a pioneer in various branches of her field, not only Zoroastrianism. She contributed to the scholarly Encyclopaedia Iranica but was also happy to write articles and entries to books for the wider public.

Mary was born in Darjeeling, India, the daughter of Anglo-Irish parents. Her father, WH Boyce, was a judge in the Indian civil service, and her mother, previously NI Gardiner, was the grand-daughter of the historian, Samuel Rawson Gardiner. Their daughter was educated at Wimbledon high school and at Cheltenham Ladies college, which she said she always hated. Mary studied English, archaeology and anthropology at Newnham College, Cambridge, where she gained a double first, and then taught Anglo-Saxon literature and archaeology at Royal Holloway College, London University.

While doing this she also studied Persian at Soas, where she met her future mentor, Professor Walter Henning. Under his inspiration she began research into Manichaeism and then, in 1947, was appointed to a new Soas lectureship in Iranian studies. Her professorship finally came after Henning's move to Berkeley in 1962, and Mary remained professor of Iranian studies until her retirement, continuing as professor emeritus until her death.

At Soas, Mary inspired numerous students who went on to hold professorships in many countries. She could be a harsh critic with tongue and pen; students and academics alike anticipated her criticisms of draft chapters or articles with trepidation. But what few know is how generous she was to students facing difficulties, either personal or financial. She was stern and demanding but also kind and supportive.

She continued her close ties with Zoroastrians, not only Iranians but also Parsees from India. The Zoroastrian Trust Funds of Europe long wanted to honour her, but she declined any honours apart from the Royal Asiatic Society's Burton memorial medal for the work which lay behind her Katrak lectures and their publication, and the Sir Percy Sykes memorial medal of the Royal Society of Asian Affairs.

A very private person, outside her academic and family concerns she had a great passion for gardening. In recent years she would hobble down into her north London garden once a week and, from her window above, relish the spectacle of each season and the abundant bird life.

She never married, being wedded - as she put it - to her academic work.

She is survived by her brother Peter, with whom she spent much of each year in Somerset, her nephew Geoffrey, and by many grateful and devoted students.